CEEQUAL Excellent – Construction Only Award
Version 4, Dec 2010 | Oxford, England
Assessor: Amy Shuffleton
The aim of the Wolvercote Viaduct scheme was to replace the existing 45-year-old, 250-metre-long, 12-span structure that carries dual two lanes over the Birmingham mainline railway, the Oxford Canal and the A40 Northern Bypass Road.
The work was to be carried out with minimum impact to the environment, the local community and the travelling public on this strategic route used by over 70,000 vehicles daily.
Prior to construction of the permanent new viaduct, a structure with a 11.9-metre-wide deck was built in a temporary location and on temporary supports adjacent to the existing viaduct. Traffic flows were adjusted to travel over the existing southbound deck and the new temporary structure. This allowed the original northbound deck to be demolished and a new deck to be built in its place. Northbound traffic flow was then moved onto the new permanent deck whilst the existing southbound deck was demolished.
After construction of the permanent southbound supports, the new 250-metre-long and 11-metre-wide deck, weighing 5000 tonnes, was slid 16 metres sideways from its temporary supports into its new permanent location on the southbound supports. Southbound traffic was then transferred onto the new permanent deck and the adjacent temporary supports were removed to just below ground level.
After completing the main connection of the new decks to the two carriageways in April 2010, the final traffic management was removed from the bridge in June 2010.
As part of the planning process for the work, numerous ecological surveys of the whole site were completed. Ecological aspects identified were subsequently managed by the site team assisted by an independent on-site Clerk of Works.
The works were carefully programmed to ensure that the main site was cleared outside the bird nesting season and that any ecological mitigation and translocation works required were completed on site minimising impact where possible.
Over 200 slow worms and grass snakes were translocated to specially prepared habitats and hibernaculars.
Other measures and habitat enhancements included:
- translocating an ancient hedgerow along the canalside bridleway to a temporary location and then planting it back in its original position
- planting over 5000 trees, shrubs and plants and seeding over 7000 square metres with locally sourced grasses
- erecting over 2000 metres of boundary fencing, including 1000 metres of temporary reptile fencing and an additional 550 metres of permanent environmental badger fencing to prevent wildlife straying onto the road
- diverting a culvert during the construction works
- erecting 9 bat boxes along the structure
- designing and constructing numerous interceptors at the base of the permanent support to manage surface water drainage from the new road and deck (surface water from the old viaduct had previously been released directly to the watercourse untreated).
Waste diversion from landfill
95% of all waste produced during the works was diverted from landfill. This equates to over 57,000 tonnes of waste being recycled. A number of methods were implemented on site to assist in diverting material from landfill.
The old bridge structure was recycled in its entirety, including concrete, reinforcement and deck. The concrete structure was crushed under the WRAP Protocol utilising relevant environmental permit exemptions. This created a usable product from the waste concrete, some of which was used in temporary works on site. The remainder was used on other sites within the local area.
Every effort was made to protect the local heritage and gather insight about the history of the area. During topsoil clearance, evidence of Roman occupation was found and the site was investigated with guidance from the County Archaeologists and the findings preserved in situ.
Two previously unknown ditches were also discovered, one dating back to medieval times and the other as far as the Roman period. This information was shared via the community noticeboard and with local schools, where the site team delivered several presentations on the proposed project outlining what had been discovered, how it was managed and the progress of the works.
Scheme benefits to road users and the general public
Disruption to road users during the works was minimised as far as possible by:
- keeping four lanes of traffic open (two each way) at all times during the day and only closing lanes/carriageways in part for essential works during the night
- using a network of CCTV cameras to monitor traffic flows and identify accidents and breakdowns, providing free vehicle recovery and a welfare facility for use by the vehicle occupants while awaiting full recovery. Nine CCTV cameras monitored over 157,680 hours and 174 breakdowns were dealt with. Vehicles recovered from the carriageway were returned to the compound in an average time of nine minutes.
- giving advance warning of works through the use local media, temporary electronic messages and the HA website to keep road users and the local community informed of carriageway closures and changes to the highway layout.
On completion of the scheme motorists using the viaduct will experience improved overall safety during their journey and greater journey time reliability. Use of the latest low-noise tarmac will also reduce stress for drivers as well as minimising noise levels for nearby residents.
Furthermore, the viaduct has been constructed utilising new and more durable techniques to minimise future disruptive maintenance.
A Community Relations Manager was appointed and multiple exhibitions and meetings were held with the local community, local authorities and other stakeholders during the planning and construction stages.
During construction, the site team hosted site visits for local residents, local schools and other interested parties, and issued newsletters and door-to-door leaflets detailing any changes to the work. The site had a dedicated information hotline with a direct connection to the project offices, providing a 24-hour, 7-days-a-week response. This allowed a personal and speedy resolution of day-to-day enquiries and complaints.
The scheme was awarded two Gold Considerate Constructors Awards for its detailed attention to considerate site practices and comprehensive communication programme, which included assisting with the transportation of cyclists and pedestrians around the area of the roadworks when cycle paths were temporarily closed, and sponsorship of a number of local causes, such as erecting new fencing, raising flower beds for a school playground, new surfacing works for a local youth club, gate refurbishment and the provision, under licence, of wood chippings for track improvements for a local farmer.
Overall, in excess of 50 letters of thanks were received for the works completed and assistance provided.